Want to control your winamp via a web browser? Install the WAWI plug-in. It works with the new Winamp 5 as well. I have been looking for something like this for a while. There is the httpQ plug-in which let you talk to winamp via http. But you still need to write some code. The WAWI plug-in let you access and control winamp immediately. It also has a directory browsing feature. So you can add songs from your library of MP3's to the playlist.
I actually have this working using the wifi NetFront browser on my Sony TH55 PDA. I can wirelessly control my music server connected to my stereo at home.